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Shark Bytes

February 2015 Shark Bytes

written by Monique Fallows

Posted on Friday, 6 March 2015

The 2015 Great White Shark Season at Seal Island has begun and after a four month break it is fantastic to see our beloved sharks again!

In our February news I’ll be writing about our shark sightings, an update on our Sharks of Southern Africa Expeditions and of special interest there is a short discussion about how the South East wind plays an important part in the vitality of False Bay.

Chris also had the privilege of spending a month exploring South Georgia in the Southern Ocean so there is also a description of his time with the magnificent Wandering Albatross.

In the last four years the Seal Island shark season has begun in early February. This is a pretty significant change since the general rule was for the season to start in April each year and as such I wasn’t too sure of what February would bring.

We did our first exploratory trip to Seal Island at the beginning of the month. Within 10 minutes we had our first shark to the boat and 30 minutes into the trip we had two very interactive sharks. Full of confidence we declared our season open and the very first trip of the season with guests on board was a great success with three sharks at the boat.

Unfortunately trip two signalled the start of a number of quieter trips and a month long battle with the dreaded South Easter wind.

We always inform our guests at this time of the year that it is early season and sightings can go either way so guests’ expectations were in check. Although as mentioned there were some quiet trips we did have a number of trips with fair sightings of one to three sharks per trip.

The highlight of the month has undoubtedly been observing the numerous scavenge events that took place on the northern side of the Island. It is our opinion that due to the over fishing of the Great White sharks’ summer diet of smaller shark species the Great Whites are perhaps looking for other alternatives.

The South Easterly wind and sea washes off many seal carcasses as well as sick and dying seals taking them in a northerly direction off Seal Island. These seals are in poor condition and do not have the same thick layer of blubber and thus the high energy yield of a six month old seal but by scavenge feeding the sharks are using very little energy to obtain the meal. So, the small amount of energy used will be worth the low energy return.

On anchor we pay particular attention to seal carcasses floating off the Island and many times we are able to witness the event.

Sadly, numerous seals seem to fall victim to a virus that affects their motor skills and these seals make large amounts of splashing on the surface as they battle to swim. They will not survive the virus so I feel it is much better for the seal if a shark finds it and is able to finish it off quickly, and at the same time the shark is benefitting. So, we have also kept a sharp lookout for these sick seals and have thus managed to witness many fascinating scavenge events close to the boat.

Of particular interest to me was a situation towards the end of the month where we observed a young sick seal making a large amount of thrashing on the surface 20 meters from the boat. At the time we had a 3.5 meter shark around the boat that quickly picked up on the presence of the seal. We watched the shark swim over for a closer investigation and were surprised to observe the shark virtually bump the seal a couple of times before moving off completely. We assume he had no interest in the easy meal whatsoever. It was a great example of how discerning the sharks can be and how capable they are of making their own decisions of what they want to eat or do not want to eat.

Good news is that the shark sightings have definitely picked up towards the end of the month and our last few trips we were seeing between four and six sharks per trip.

Another interesting observation that compares with the early 2014 season is that we recorded mostly male sharks present at Seal Island. We don’t see a lot of sexual segregation at Seal Island so this observation is of particular interest.

This magnificent animal is the largest sting ray in the world and can get to 2.1 meters wide and weigh up to 350kgs!

The Importance of the South Easterly Wind

We have had an extremely windy summer in Cape Town this year, so much so that I hardly feel as though we have had a summer. It’s hard to believe the wind is important, but in actual fact it is vital to creating conditions for healthy marine life in False Bay.

Through many field seasons, reading and research I have tried to understand how the whole system in False Bay and its surrounds work.

The South Easter is an offshore wind in certain west facing parts of the Bay and initially blows warm surface water away from the inshore area and into False Bay. Due to the currents in the Bay this water is circulated within the Bay and then eventually cycled out with constant replacement of other water as the wind continues to blow.

Strong upwelling, created by the wind, eventually brings deep water which is normally colder and richer in nutrients to the surface. Now that these nutrients are close to the surface they are exposed to sunlight and ideal conditions are created for the growth of phyto plankton through photosynthesis.

Through many field seasons, reading and research I have tried to understand how the whole system in False Bay and its surrounds work.

The plankton of course is the first link in the food chain and is the food source for bait fish that triggers the rest of the food chain in the Bay. Everything from gamefish to other shark species to dolphins, Bydes whales and Cape Gannets feed on baitfish and these species make up different trophic levels in the food chain. As the wind blows and the currents cycle this water through the Bay everything gains momentum.

As such we have had great sightings of common dolphin with some schools up to 800 strong. A number of Brydes whales have been recorded and gannet numbers are increasing.

Unfortunately the nutrient rich water is also responsible for some of the dirtiest and poorest water visibility I have seen for some time at Seal Island. Pea soup is a flattering description of the water colour so surface viewing has definitely been the best option for the great white sharks these past few weeks.

The above explanation could also be a clue to our slow sightings at Seal Island… there is undoubtedly a good selection of smaller shark species closer to shore and perhaps a better food option for the Great white sharks at this particular time.

Sharks of Southern Africa Expedition 2015

We have just finished two back to back Sharks of Southern Africa Expeditions. This expedition focuses on seeing many different shark species over a 10 day period. This includes everything from Great White sharks to Puff Adder shy sharks as well as enjoying whatever other marine life we are fortunate to come across. For the full trip report from Chris please read here.

The surprise highlight for me was a couple of very shallow and protected dives in the kelp forest. Due to the relentless wind that was blowing this was really our only option but it turned out to be a huge amount of fun. The intention was to see all the smaller Cat shark species and had great success with big and small Striped Cat sharks Porodermaafricanum, commonly called Pyjama shark. The biggest ones were mature animals at just under 1 meter which is a big as they get. We saw about 10 different Striped Cat sharks per dive as well as a few Puff Adder shy sharks Haploblepharusedwardsii and Brown shy sharks Haploblepharusfuscus that managed to weasel their way in. We even spotted the rare (due to its restricted range) Leopard Cat shark Porodermapantherrinum which we all got a great look at.

The middle of both dives signalled the arrival of a number of hugely impressive Short-tailed devil rays Dasyatisbrevicaudata. This magnificent animal is the largest sting ray in the world and can get to 2.1 meters wide and weigh up to 350kgs! I was so excited to finally have a really good look at these guys underwater and really enjoyed diving down and holding onto a piece of kelp as they gently and gracefully glided by. This was really a great reminder to me how sometimes just doing small simple things can give you such great enjoyment!

I also want to say a special thank you to the Expedition participants. It was fantastic spending time with all of you and to see how excited you all were with the various wildlife we came across.

2015 APEX SPECIAL EXPEDITIONS

Speaking of Special Expeditions I’d like to gently remind all of you of some of our exciting shark and marine wildlife expeditions planned for our 2015 season.

This is our premier expedition of the year and focuses on observing and photographing the unique and spectacular predatory events at Seal Island. The expedition is limited to 8 guests per expedition and this small focused group means that we can really make the most of observing this special hunting behaviour.

A great opportunity to learn from our host Dr Neil Hammerschlag over a time period that is great for predatory behaviour as well as good cage diving conditions.

The Wanderer

Chris had the unique opportunity of spending one month on the world famous wildlife island of South Georgia in the southern ocean. He was part of an expedition team to count wandering albatross that takes place every 10 years. This allowed him access to restricted areas and of course very intimate and special time spent with these great ocean birds.

Please read here for his first impressions of the Wandering Albatross. It’s a must for all bird and true nature lovers!